Regular arrays of metallic or semiconductor nanoscale pillars and rings having sizes below 100 nm have recently attracted attention due to their unique optical, electrical and magnetic properties. Different strategies have been used for the fabrication of such arrays, including photon and electric beam lithography, self assembly of nanospheres or replication by embossing, molding or printing with master stamps. In the case of self assembly, the arrangement of the nanoscale structures is often random, or organized in reduced areas. The replication using master stamps has demonstrated feature sizes below 100 nm and large area coverage. However, a different master is required for each pattern, thereby restricting the versatility of the method.
An approach commonly used to print nanoscale periodic features is interferometric lithography (IL). This maskless photolithography technique is based on the activation of a photoresist by the interference pattern generated by two or more spatially coherent light beams. IL can efficiently print periodic patterns in a sensitive photoresist coated substrate with resolution approaching half of the wavelength of the illumination. In this approach, reducing the wavelength of the illumination provides a direct and simple path to realizing interference patterns having dimensions of tens of nanometers and below. This has been the principal motivation for using ultraviolet, shorter wavelength extreme ultraviolet light (EUV) or soft x-ray light (SXR) for such applications. The versatility of EUV/SXR IL for patterning different patterns and realizing small features has been demonstrated using 13 nm wavelength light from a synchrotron source. However, the widespread use of this technique in applications requires its implementation on a more compact and readily accessible apparatus.
Accordingly, it is an object of the present invention to provide an apparatus and method for patterning nanoscale features in materials by lithography using extreme ultraviolet/soft x-ray (EUV/SXR) interferometry.
Additional objects, advantages and novel features of the invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.